1. Field of the Invention
The present invention relates to a method of manufacturing an organic light emitting device.
2. Description of the Related Art
As a method of patterning an organic compound layer including an emission layer constituting an organic light emitting element, in recent years, a method using photolithography has drawn attention because the method is capable of performing high-precision patterning compared with other patterning procedures such as those using a metal mask.
For example, Japanese Patent No. 4578026 discloses a method of patterning an organic compound layer through use of photolithography. In Japanese Patent No. 4578026, specifically, a light emitting device including multiple organic electroluminescent elements is manufactured in accordance with a method described below. First, a thin film layer to be a first emission layer insoluble in a photoresist material is formed on a base, a photoresist layer is formed on the thin film layer, and then, the photoresist layer is patterned so that the photoresist layer remains in a portion in which a first light emitting portion is to be formed. Next, after the thin film layer provided in an area where the photoresist layer does not remain is removed, a second emission layer is formed on the base having the first emission layer and the photoresist layer remaining on the surface of the first emission layer. After that, release agent is brought into contact with the remaining photoresist layer to peel the photoresist layer together with the second emission layer formed on the photoresist layer. Accordingly, the first light emitting portion and a second light emitting portion formed in an intended pattern shape are obtained.
Japanese Patent No. 4544811 also describes a manufacturing process substantially similar to that of Japanese Patent No. 4578026. Further, Japanese Patent No. 4544811 discloses that a release layer is provided between an organic compound layer and a resist layer. Herein, the release layer refers to a layer to be provided so as to peel a member such as a photoresist layer easily, and, in particular, the release layer is used in the case where it is difficult to peel a member such as a photoresist layer from an organic compound layer including an emission layer.
In a process of peeling a patterned photoresist layer from an organic compound layer directly or through use of a release layer as in Japanese Patent Nos. 4578026 and 4544811, a method of dissolving and peeling a constituent material of a predetermined layer through use of a solution for dissolving the constituent material is employed. Specifically, a photoresist layer and a release layer are brought into contact with a solution (release agent) for dissolving the photoresist layer and the release layer to dissolve the photoresist layer and the release layer. In this case, as the release agent, liquid for selectively dissolving the photoresist layer or the release layer (hereinafter collectively referred to as “release layer”) is used. In this case, it is necessary to allow the solution to sufficiently permeate the release layer. However, there is a problem in that a layer to be formed on the release layer has a low solution rate with respect to the release agent, and hence the release agent does not easily permeate the release layer from an upper portion thereof. Therefore, the release agent permeates the release layer from an end portion thereof. In the case where an area to be peeled is large, the solution does not sufficiently permeate the release layer, and as a result, there arises a problem in that a residue of the release layer is formed.
In general, the release layer is patterned by forming, on the release layer, a mask pattern with a layer capable of forming a pattern through photolithography. In this case, the layer capable of forming a pattern through photolithography refers to a layer which is formed of at least one layer and exhibits resistance during pattern formation of the release layer.
Although Japanese Patent Nos. 4578026 and 4544811 do not particularly mention a specific pattern shape of the organic compound layer, it can be thought that the pattern shape of the organic compound layer depends on a pattern shape of the release layer. The release layer provided in a light emitting region is generally patterned to a size of several μm to hundreds of μm although depending on the screen size, and hence, the release agent permeates the entire release layer sufficiently from an end portion of each pattern. In contrast, a portion other than the light emitting region has no or less minute patterns described above. Therefore, even when an attempt is made to allow the release agent to permeate the release layer from an end portion of a pattern, the release agent does not permeate a pattern center portion of the release layer easily, and the release layer cannot be peeled sufficiently, with the result that a residue may be formed. For example, when a residue of the release layer connecting the outside to the light emitting region is formed in the case where an encapsulation member or an encapsulation film for encapsulating the light emitting region from the outside is provided, the residue functions as a water intrusion path, which causes an encapsulation defect.